Cellular differentiation, growth, function and death are regulated by a complex network of mechanisms at the molecular level in a multicellular organism. In the healthy animal or human, these mechanisms allow the cell to carry out its designed function and then die at a programmed rate.
Abnormal cellular proliferation, notably hyperproliferation, can occur as a result of a wide variety of factors, including genetic mutation, infection, exposure to toxins, autoimmune disorders, and benign or malignant tumor induction.
There are a number of skin disorders associated with cellular hyperproliferation. Psoriasis, for example, is a benign disease of human skin generally characterized by plaques covered by thickened scales. The disease is caused by increased proliferation of epidermal cells of unknown cause. In normal skin the time required for a cell to move from the basal layer to the upper granular layer is about five weeks. In psoriasis, this time is only 6 to 9 days, partially due to an increase in the number of proliferating cells and an increase in the proportion of cells which are dividing (G. Grove, Int. J. Dermatol. 18:111, 1979). Approximately 2% of the population the United States have psoriasis, occurring in about 3% of Caucasian Americans, in about 1% of African Americans, and rarely in native Americans. Chronic eczema is also associated with significant hyperproliferation of the epidermis. Other diseases caused by hyperproliferation of skin cells include atopic dermatitis, lichen planus, warts, pemphigus vulgaris, actinic keratosis, basal cell carcinoma and squamous cell carcinoma.
Other hyperproliferative cell disorders include blood vessel proliferation disorders, fibrotic disorders, autoimmune disorders, graft-versus-host rejection, tumors and cancers.
Blood vessel proliferative disorders include angiogenic and vasculogenic disorders. Proliferation of smooth muscle cells in the course of development of plaques in vascular tissue cause, for example, restenosis, retinopathies and atherosclerosis. The advanced lesions of atherosclerosis result from an excessive inflammatory-proliferative response to an insult to the endothelium and smooth muscle of the artery wall (Ross R., Nature 362:801-809 (1993)). Both cell migration and cell proliferation play a role in the formation of atherosclerotic lesions.
Fibrotic disorders are often due to the abnormal formation of an extracellular matrix. Examples of fibrotic disorders include hepatic cirrhosis and mesangial proliferative cell disorders. Hepatic cirrhosis is characterized by the increase in extracellular matrix constituents resulting in the formation of a hepatic scar. Hepatic cirrhosis can cause diseases such as cirrhosis of the liver. An increased extracellular matrix resulting in a hepatic scar can also be caused by viral infection such as hepatitis. Lipocytes appear to play a major role in hepatic cirrhosis.
Mesangial disorders are brought about by abnormal proliferation of mesangial cells. Mesangial hyperproliferative cell disorders include various human renal diseases, such as glomerulonephritis, diabetic nephropathy, malignant nephrosclerosis, thrombotic microangiopathy syndromes, transplant rejection, and glomerulopathies.
Another disease with a proliferative component is rheumatoid arthritis. Rheumatoid arthritis is generally considered an autoimmune disease that is thought to be associated with activity of autoreactive T cells (See, e.g., Harris, E. D., Jr., The New England Journal of Medicine, 322: 1277-1289 (1990)), and to be caused by autoantibodies produced against collagen and IgE.
Other disorders that can include an abnormal cellular proliferative component include Behcet's syndrome, acute respiratory distress syndrome (ARDS), ischemic heart disease, post-dialysis syndrome, leukemia, acquired immune deficiency syndrome, vasculitis, lipid histiocytosis, septic shock and inflammation in general.
A tumor, also called a neoplasm, is a new growth of tissue in which the multiplication of cells is uncontrolled and progressive. A benign tumor is one that lacks the properties of invasion and metastasis and is usually surrounded by a fibrous capsule. A malignant tumor (i.e., cancer) is one that is capable of both invasion and metastasis. Malignant tumors also show a greater degree of anaplasia (i.e., loss of differentiation of cells and of their orientation to one another and to their axial framework) than benign tumors.
Approximately 1.2 million Americans are diagnosed with cancer each year, 8,000 of which are children. In addition, 500,000 Americans die from cancer each year in the United States alone. Prostate and lung cancers are the leading causes of death in men while breast and lung cancer are the leading causes of death in women. It is estimated that cancer-related costs account for about 10 percent of the total amount spent on disease treatment in the United States.
Proliferative disorders are currently treated by a variety of classes of compounds including alkylating agents, antimetabolites, natural products, enzymes, biological response modifiers, miscellaneous agents, hormones and antagonists, such as those listed below.
Alkylating Agents
Nitrogen Mustards: Mechlorethamine (Hodgkin's disease, non-Hodgkin's lymphomas), Cyclophosphamide Ifosfamide (acute and chronic lymphocytic leukemias, Hodgkin's disease, non-Hodgkin's lymphomas, multiple myeloma, neuroblastoma, breast, ovary, lung, Wilms' tumor, cervix, testis, soft-tissue sarcomas), Melphalan (L-sarcolysin) (multiple myeloma, breast, ovary), Chlorambucil (chronic lymphoctic leukemia, primary macroglobulinemia, Hodgkin's disease, non-Hodgkin's lymphomas).
Ethylenimines and Methylmelamines: Hexamethylmelamine (ovary), Thiotepa (bladder, breast, ovary).
Alkyl Sulfonates: Busulfan (chronic granuloytic leukemia).
Nitrosoureas: Carmustine (BCNU) (Hodgkin's disease, non-Hodgkin's lymphomas, primary brain tumors, multiple myeloma, malignant melanoma), Lomustine (CCNU) (Hodgkin's disease, non-Hodgkin's lymphomas, primary brain tumors, small-cell lung), Semustine (methyl-CCNU) (primary brain tumors, stomach, colon), Streptozocin (streptozocin) (malignant pancreatic insulinoma, malignant carcinoin).
Triazenes: Dacarbazine (DTIC; dimethyltriazenoimid-azolecarboxamide) (malignant melanoma, Hodgkin's disease, soft-tissue sarcomas).
Antimetabolites
Folic Acid Analogs: Methotrexate(amethopterin) (acute lymphocytic leukemia, choriocarcinoma, mycosis fungoides, breast, head and neck, lung, osteogenic sarcoma).
Pyrimidine Analogs: Fluorouracil (5-fluorouracil; 5-FU) Floxuridine (fluorodeoxyuridine; FUdR) (breast, colon, stomach, pancreas, ovary, head and neck, urinary bladder, premalignant skin lesions) (topical), Cytarabine(cytosine arabinoside) (acute granulocytic and acute lymphocytic leukemias).
Purine Analogs and Related Inhibitors: Mercaptopurine (6-mercaptopurine; 6-MP) (acute lymphocytic, acute granulocytic and chronic granulocytic leukemia), Thioguanine (6-thioguanine: TG) (acute granulocytic, acute lymphocytic and chronic granulocytic leukemia), Pentostatin (2′-deoxycyoformycin) (hairy cell leukemia, mycosis fungoides, chronic lymphocytic leukemia).
Vinca Alkaloids: Vinblastine (VLB) (Hodgkin's disease, non-Hodgkin's lymphomas, breast, testis), Vincristine (acute lymphocytic leukemia, neuroblastoma, Wilms' tumor, rhabdomyosarcoma, Hodgkin's disease, non-Hodgkin's lymphomas, small-cell lung).
Epipodophyl-lotoxins: Etoposide (testis, small-cell lung and other lung, breast, Hodgkin's disease, non-Hodgkin's lymphomas, acute granulocytic leukemia, Kaposi's sarcoma), Teniposide (testis, small-cell lung and other lung, breast, Hodgkin's disease, non-Hodgkin's lymphomas, acute granulocytic leukemia, Kaposi's sarcoma).
Natural Products
Antibiotics: Dactinomycin (actinonmycin D) (choriocarcinoma, Wilms' tumor rhabdomyosarcoma, testis, Kaposi's sarcoma), Daunorubicin (daunomycin; rubidomycin) (acute granulocytic and acute lymphocytic leukemias), Doxorubicin (soft tissue, osteogenic, and other sarcomas; Hodgkin's disease, non-Hodgkin's lymphomas, acute leukemias, breast, genitourinary thyroid, lung, stomach, neuroblastoma), Bleomycin (testis, head and neck, skin and esophagus lung, and genitourinary tract, Hodgkin's disease, non-Hodgkin's lymphomas), Plicamycin (mithramycin) (testis, malignant hypercalcema), Mitomycin (mitomycin C) (stomach, cervix, colon, breast, pancreas, bladder, head and neck).
Enzymes: L-Asparaginase (acute lymphocytic leukemia).
Biological Response Modifiers: Interferon-alfa (hairy cell leukemia, Kaposi's sarcoma, melanoma, carcinoid, renal cell, ovary, bladder, non Hodgkin's lymphomas, mycosis fungoides, multiple myeloma, chronic granulocytic leukemia).
Hormones and Antagonists
Estrogens: Diethylstibestrol Ethinyl estradiol (breast, prostate)
Antiestrogen: Tamoxifen (breast).
Androgens: Testosterone propionate Fluxomyesterone (breast).
Antiandrogen: Flutamide (prostate).
Gonadotropin-Releasing Hormone Analog: Leuprolide (prostate).
Miscellaneous Agents
Platinum Coordination Complexes: Cisplatin (cis-DDP) Carboplatin (testis, ovary, bladder, head and neck, lung, thyroid, cervix, endometrium, neuroblastoma, osteogenic sarcoma).
Anthracenedione: Mixtozantrone (acute granulocytic leukemia, breast).
Substituted Urea: Hydroxyurea (chronic granulocytic leukemia, polycythemia vera, essential thrombocytosis, malignant melanoma).
Methylhydrazine Derivative: Procarbazine (N-methylhydrazine, MIH) (Hodgkin's disease).
Adrenocortical Suppressant: Miotane (o,p′-DDD) (adrenal cortex), Aminoglutethimide (breast).
Adrenorticosteriods: Prednisone (acute and chronic lymphocytic leukemias, non-Hodgkin's lymphomas, Hodgkin's disease, breast).
Progestins: Hydroxprogesterone caproate, Medroxyprogersterone acetate, Megestrol acetate (endometrium, breast).
Toxicity associated with therapy for abnormally proliferating cells, including cancer, is due in part to a lack of selectivity of the drug for diseased versus normal cells. To overcome this limitation, therapeutic strategies that increase the specificity and thus reduce the toxicity of drugs for the treatment of proliferative disorders are being explored. One such strategy that is being aggressively pursued is drug targeting.
An objective of treatment and/or image targeting is to deliver a therapeutic and/or diagnostic agent to a specific site of action through a carrier system. Targeting achieves at least two major aims of drug delivery. The first is to deliver the maximum dose of therapeutic agent to diseased cells. The second is the avoidance of uptake by normal, healthy cells. Thus, targeted drug delivery systems result in enhancing drug accumulation in the proliferative cells while decreasing exposure to healthy tissues. As such, the efficacy is increased while the toxicity is decreased, giving a better therapeutic index.
Two classes of compounds that are known to localize in malignant tumors are the porphyrins and the related phthalocyanines. The biochemical basis by which these compounds achieve elevated concentration in malignant tumors is unknown, but this observation has served as the rationale for the use of hematoporphyrin derivatives in the photodyamic therapy of cancer (Dougherty, T. J. et al., Porphyrin Photosensitization, 3-13, New York: Plenum Publishing Corp. (1981)).
Cells undergoing rapid proliferation have been shown to increase uptake of thymidine and methionine. (See, for example, M. E. van Eijkeren et al., Acta Oncologica, 31, 539 (1992); K. Kobota et al., J. Nucl. Med., 32, 2118 (1991) and K. Higashi et al., J. Nucl. Med., 34, 773 (1993)). Since methylcobalamin is directly involved with methionine synthesis and indirectly involved in the synthesis of thymidylate and DNA, methyl-cobalamin as well as Cobalt-57-cyanocobalamin have also been shown to have increased uptake in rapidly dividing tissue (for example, see, B. A. Cooper et al., Nature, 191, 393 (1961); H. Flodh, Acta Radiol. Suppl., 284, 55 (1968); L. Bloomquist et al., Experientia, 25, 294 (1969)). Additionally, upregulation in the number of transcobalamin II receptors has been demonstrated in several malignant cell lines during their accelerated thymidine incorporation and DNA synthesis. See, J. Lindemans et al., Exp. Cell. Res., 184, 449 (1989); T. Amagasaki et al., Blood, 26, 138 (1990) and J. A. Begly et al., J. Cell Physiol., 156, 43 (1993). Bacteria naturally insert Cobalt-59 into the corrin ring of vitamin B12. Commercially this has been exploited by the fermentative production of Co-56, Co-57, Co-58, and Co-60 radiolabeled vitamin B12. For example, see Chaiet et al., Science, 111, 601 (1950). Unfortunately Cobalt-57, with a half life of 270.9 days, makes Co-57-cyanocobalamin unsuitable for clinical tumor imaging. Other metal ions (cobalt, copper and zinc) have been chemically inserted into naturally occurring descobaltocorrinoids produced by Chromatium and Streptomyces olivaceous. Attempts to chemically insert other metal ions in these cobalt free corrinoid rings have been unsuccessful. The placement of metals (cobalt, nickel, palladium, platinum, rhodium, zinc, and lithium) into a synthetic corrin ring has not presented any major difficulties. However, their instability and cost to produce makes them impractical for biological assays. Although Co-59 has a weakly paramagnetic quadrapolar nucleus in the 2+ oxidation state, Co-59 exists in the 3+ oxidation state within the corrin ring of vitamin B12 and is diamagnetic. Therefore, insertion of either a radioactive or paramagnetic metal ion other than cobalt into the corrin ring does not seem feasible at this time.
The structure of various forms of vitamin B12 is shown in FIG. 1, wherein X is CN, OH, CH3 or 5′-deoxyadenosyl, respectively. The term cobalamin is sometimes used to refer to the entire molecule except the X group. The fundamental ring system without cobalt (Co) or side chains is called corrin and the octadehydrocorrin is called corrole. FIG. 1 is adapted from The Merck Index, Merck & Co. (11th ed. 1989), wherein X is above the plane defined by the corrin ring and the nucleotide is below the plane of the ring. The corrin ring has attached seven amidoalkyl (H2NC(O)Alk) substituents, at the 2, 3, 7, 8, 13, 18 and 23 positions, which can be designated a-g respectively. See D. L. Anton et al., J. Amer. Chem. Soc., 102, 2215 (1980). The 2, 3, 7, 8 and 13 positions are shown in FIG. 1 as positions a-e, respectively.
For several years after the isolation of vitamin B12 as cyanocobalamin in 1948, it was assumed that cyanocobalamin and possibly hydroxocobalamin, its photolytic breakdown product, occurred in man. Since then it has been recognized that cyanocobalamin is an artifact of the isolation of vitamin B12 and that hydroxocobalamin and the two coenzyme forms, methylcobalamin and adenosylcobalamin, are the naturally occurring forms of the vitamin.
Vitamin B12 (adenosyl-, cyano-, hydroxo- or methylcobalamin) must be bound by the transport protein Transcobalamin I, II, or III (“TC”) to be biologically active, and by Intrinsic Factor (“IF”) if administered orally. Gastrointestinal absorption of vitamin B12 occurs when the intrinsic factor-vitamin B12 complex is bound to the intrinsic factor receptor in the terminal ileum. Likewise, intravascular transport and subsequent cellular uptake of vitamin B12 throughout the body typically occurs through the transcobalamin transport protein (I, II or III) and the cell membrane transcobalamin receptors, respectively. After the transcobalamin vitamin B12 complex has been internalized in the cell, the transport protein undergoes lysozymal degradation, which releases vitamin B12 into the cytoplasm. All forms of vitamin B12 can then be interconverted into adenosyl-, hydroxo- or methylcobalamin depending upon cellular demand. See, for example, A. E. Finkler et al., Arch. Biochem. Biophys., 120, 79 (1967); C. Hall et al., J. Cell Physiol., 133, 187 (1987); M. E. Rappazzo et al., J. Clin. Invest., 51, 1915 (1972) and R. Soda et al., Blood, 65, 795 (1985).
A process for preparing 125I-vitamin B12 derivatives is described in Niswender et al. (U.S. Pat. No. 3,981,863). In this process, vitamin B12 is first subjected to mild hydrolysis to form a mixture of monocarboxylic acids, which Houts, infra, disclosed to contain mostly the (e)-isomer. The mixture is then reacted with a p-(aminoalkyl)phenol to introduce a phenol group into the B12 acids (via reaction with one of the free carboxylic acid groups). The mixed substituent B12 derivatives are then iodinated in the phenol-group substituent. This U.S. patent teaches that the mixed 125I-B12 derivatives so made are useful in the radioimmunoassay of B12, using antibodies raised against the mixture.
T. M. Houts (U.S. Pat. No. 4,465,775) reported that the components of the radiolabeled mixture of Niswender et al. did not bind with equal affinity to IF. Houts disclosed that radioiodinated derivatives of the pure monocarboxylic (d)-isomer are useful in assays of B12 in which IF is used.
U.S. Pat. Nos. 5,739,313; 6,004,533; 6,096,290 and PCT Publication WO 97/18231 listing Collins and Hogenkamp as inventors disclose radionuclide labeling of vitamin B12 through the propionamide moieties on naturally occurring vitamin B12. The inventors converted the propionamide moieties at the b-, d-, and e-positions of the corrole ring to monocarboxylic acids, through a mild hydrolysis, and separated the carboxylic acids by column chromatography. The inventors then attached a bifunctional linking moiety to the carboxylate function through an amide linkage, and a chelating agent to the linking moiety again through an amide linkage. The chelating moiety was then used to attach a radionuclide to the vitamin that can be used for therapeutic and/or diagnostic purposes. See also PCT Publications WO 00/62808; WO 01/28595 and WO 01/28592.
PCT Publication WO 98/08859 listing Grissom et al as inventors discloses conjugates containing a bioactive agent and an organocobalt complex in which the bioactive agent is covalently bound directly or indirectly, via a spacer, to the cobalt atom. The organocobalt complex can be cobalamin and the bioactive agent can be a chemotherapeutic agent. However, only one bioactive agent (i.e., chemotherapeutic agent) is attached to the organocobalt complex (i.e., cobalamin) and the attachment is solely through the cobalt atom (i.e., the 6-position of cobalamin). The bioactive agent is released from the bioconjugate by the cleavage of the weak covalent bond between the bioactive agent and the cobalt atom as a result of normal displacement by cellular nucleophiles or enzymatic action, or by application of an external signal (e.g., light, photoexcitation, ultrasound, or the presence of a magnetic field).
U.S. Pat. Nos. 5,428,023; 5,589,463 and 5,807,823 to Russell-Jones et al. discloses a vitamin B12 conjugate for delivering oral hormone formulations. Russell-Jones teaches that the vitamin B12 conjugate must be capable of binding in vivo to intrinsic factor, enabling uptake and transport of the complex from the intestinal lumen of a vertebrate host to the systemic circulation of the host. The hormones are attached to the vitamin B12 through a hydrolyzed propionamide linkage on the vitamin. The patent states that the method is useful for orally administering hormones, bioactive peptides, therapeutic agents, antigens, and haptens, and lists as therapeutic agents neomycin, salbutamol cloridine, pyrimethamine, penicillin G, methicillin, carbenicillin, pethidine, xylazine, ketamine hydrochloride, mephanesin and iron dextran. U.S. Pat. No. 5,548,064 to Russell-Jones et al. discloses a vitamin B12 conjugate for delivering erythropoietin and granulocyte-colony stimulating factor, using the same approach as the '023 patent.
U.S. Pat. No. 5,449,720 to Russell-Jones et al discloses vitamin B12 linked through a polymer to various active agents wherein the conjugate is capable of binding to intrinsic factor for systemic delivery. In particular, the document discloses the attachment of various polymeric linkers to the propionamide positions of the vitamin B12 molecule, and the attachment of various bioactive agents to the polymeric linker. Exemplary bioactive agents include hormones, bioactive peptides and polypeptides, antitumor agents, antibiotics, antipyretics, analgesics, antiinflammatories, and haemostatic agents. Exemplary polymers include carbohydrates and branched chain amino acid polymers. The linkers used in '720 are polymeric. Importantly, the linkers are described as exhibiting a mixture of molecular weights, due to the polymerization process by which they are made. See in particular, page 11, lines 25-26 wherein it is stated that the polymer used in that invention is of uncertain size and/or structure.
PCT Publication WO 99/65930 to Russell-Jones et al. discloses the attachment of various agents to the 5′-OH position on the vitamin B12 ribose ring. The publication indicates that the system can be used to attach polymers, nanoparticles, therapeutic agents, proteins and peptides to the vitamin. See also, U.S. Pat. No. 6,262,253 “Vitamin B12 conjugates with GCSF, analogues thereof and pharmaceutical compositions;” U.S. Pat. No. 6,221,397 “Surface cross-linked particles suitable for controlled delivery;” U.S. Pat. No. 6,159,502 “Oral delivery systems for microparticles;” U.S. Pat. No. 6,150,341 “Vitamin B12 derivatives and methods for their preparation;” U.S. Pat. No. 5,869,466 “Vitamin B12 mediated oral delivery systems for GCSF;” and U.S. Pat. No. 5,548,064 “Vitamin B12 conjugates with EPO, analogues thereof and pharmaceutical compositions.”
U.S. Pat. No. 5,574,018 to Habberfield et al. discloses conjugates of vitamin B12 in which a therapeutically useful protein is attached to the primary hydroxyl site of the ribose moiety. The patent lists erythropoietin, granulocyte-colony stimulating factor and human intrinsic factor as therapeutically useful proteins, and indicates that the conjugates are particularly well adapted for oral administration.
U.S. Pat. No. 5,840,880 to Morgan, Jr. et al. discloses vitamin B12 conjugates to which are linked receptor modulating agents, which affect receptor trafficking pathways that govern the cellular uptake and metabolism of vitamin B12. The receptor modulating agents are linked to the vitamin at the b-, d-, or e-position.
Other patent filings which describe uses of Vitamin B12 include U.S. Pat. No. 3,936,440 to Nath (Method of Labeling Complex Metal Chelates with Radioactive Metal Isotopes); U.S. Pat. No. 4,209,614 to Bernstein et al., (Vitamin B12 Derivatives Suitable for Radiolabeling); U.S. Pat. No. 4,279,859 (Simultaneous Radioassay of Folate and Vitamin B12); U.S. Pat. No. 4,283,342 to Yollees (Anticancer Agents and Methods of Manufacture); U.S. Pat. No. 4,301,140 to Frank et al (Radiopharmaceutical Method for Monitoring Kidneys); U.S. Pat. No. 4,465,775 to Houts (Vitamin B12 and labeled Derivatives for Such Assay); U.S. Pat. No. 5,308,606 to Wilson et al (Method of Treating and/or Diagnosing Soft Tissue Tumors); U.S. Pat. No. 5,405,839 (Vitamin B12 Derivative, Preparation Process Thereof, and Use Thereof); U.S. Pat. No. 5,449,720 to Russell-Jones et al., (Amplification of the Vitamin B12 Uptake System Using Polymers); U.S. Pat. No. 5,589,463 to Russell Jones (Oral Delivery of Biologically Active Substances Bound to Vitamin B12); U.S. Pat. No. 5,608,060 to Axworthy et al (Biotinidase-Resistant Biotin-DOTA Conjugates); U.S. Pat. No. 5,807,832 to Russell-Jones et al (Oral Delivery of Biologically Active Substances Bound to Vitamin B12); U.S. Pat. No. 5,869,465 to Morgan et al (Method of Receptor Modulation and Uses Therefor); U.S. Pat. No. 5,869,466 to Russell-Jones et al (vitamin B12 Mediated Oral Delivery systems for GCSF).
See also Ruma Banerjee, Chemistry and Biochemistry of B12 John Wiley & Sons, Inc. (1999), and in particular Part II, Section 15 of that book, entitled “Diagnostics and Therapeutic Analogues of Cobalamin,” by H. P. C. Hogenkamp, Douglas A. Collins, Charles B. Grissom, and Frederick G. West.
Despite the above findings, there remains a need for new compounds, compositions and methods to administer therapeutic and/or diagnostic agents that have improved specificity, i.e., which can localize the active agent efficiently in proliferating cells in high concentration compared to normal cells.
It is therefore an object of the invention to provide new compounds and compositions for the treatment, prophylaxis and/or diagnosis of abnormal cellular proliferation.
It is another object of the present invention to provide new methods, including surgical and medical methods, for the treatment, prophylaxis and/or diagnosis of proliferative conditions.